An application's object is programmatically referred to
as a parent when it can host, hold, or carry other objects. For this reason,
such a window is also referred to as a container. Although the first object
that comes in mind is the form, this is not the only window that can act as
parent. This means that, in your application programming adventure, you will
get acquainted with various types of containers and they are meant to play
different roles.

In some cases, two or more containers can be used to
implement the same functionality. In some other cases, your choice will be
narrowed based on your goal.

The most common and the most widely used container is
the form. In an application, a form can be configured to display like a
regular dialog box, to become a Single Document Interface (SDI) or to
participate in a Multiple Document Interface (MDI) application.

As mentioned already, there are two categories of
controls: parents and children:

Parent: The child controls are positioned on a parent. To keep
track of its children, a parent control has the Controls
property. To create a control inside of a parent, a child control is
added to the Controls property of the parent using the
Controls.Add() method. When a parent control is created, it "gives
life" to other windows that can depend on it. When a parent is
destroyed, it also destroys its children. A parent control "carries",
"holds", or hosts the controls positioned on it. When a parent is
created, made active, or made visible, it gives existence and
visibility to its controls. When a parent gets hidden, it also hides
its controls. If a parent moves, it moves with its children. The
controls keep their positions and dimensions inside the parent. The
.NET Framework provides various parent controls.

Child: A window is referred to as child when its existence, its
visibility, and its availability depend on another window referred to
as its parent. Except for the forms, all of the Windows controls you
will use in your applications are child controls and they must be
parented by another control.

A child window can be a parent of another control. For
example, the Standard toolbar of Visual Studio 2005 is the parent of the
buttons on it. If you close or hide the toolbar, its children disappear.
At the same time, the toolbar is a child of the application's form. If you
close the application, the toolbar disappears, along with its own
children. In this example, the toolbar is a child of the form but is a
parent to its buttons.

Using a Parent Control

The type of container you want to use dictates how you
acquire that container and add it to your application. Parent controls are
somewhat divided in two broad categories: primary parents and intermediate
parents. Once you have spent time with them, you will decide which one and
when to use a particular control.

The primary type of control parenting you will use is
a form. This is used as the platform for other controls, including other
containers. Therefore, when you start your application, you first decide
on the type of application. If you create a Windows Forms application, it
gets automatically equipped with a form on which you can add child
controls. When the application executes, it can present its contents to
the user:

The second category of parents you will encounter
qualify as intermediate. Theses containers cannot be the base of an
application as does the form. These parents must be positioned on another
parent first, then they can host their own children. An example of such a
parent is the property page also called tab control. This control must be
hosted by a form or dialog box. Here is an example of a property sheet
(dialog box) that hosts three property pages (tab controls) and each
property page hosts its own child controls:

Another type of intermediary container is the toolbar
that is usually used to host various buttons.

Introduction to Dialog Boxes

Description

A dialog box is a form defined with particular
properties. Like a form, a dialog box is referred to as a container. Like
a form, a dialog box is mostly used to host child controls, insuring the
role of dialog between the user and the machine. Here is an example of a
dialog box:

A dialog box has the following characteristics:

The only system button it is equipped with is Close
.
As the only system button, this button allows the user to dismiss the
dialog and ignore whatever the user would have done on the dialog box

It cannot be minimized, maximized, or restored. A dialog box does
not have any other system button but Close

It is usually modal, in which case the user is not allowed to
continue any other operation on the same application until the dialog
box is dismissed

It provides a way for the user to close or dismiss it

Practical
Learning: Introducing Dialog Boxes

Start Microsoft Visual Basic and create a new Windows Application
named SolasPropertyRental1

From the Common Controls section of the Toolbox, click ListView
and click the form

While the list view is still selected, in the Properties window,
change the following characteristics(Name): LvwPropertiesView: Details

Still in the Properties window, click Columns and click its
ellipsis button

In the ColumnHeader Collection Editor, click Add

In the right list, click Text and type Property #

Click Add.In the right list, click Text and type Property
Type

Click Add.In the right list, click Text and type Bedrooms

Click Add.In the right list, click Text and type Bathrooms

Click Add.In the right list, click Text and type Monthly
Rent

Click OK

Complete the design of the form as follows:

Control

Text

Name

ListView

Button

New Property...

BtnNewProperty

Button

Close

BtnClose

To add another form to the project, on the main menu, click
Project -> Add Windows Form...

In the middle list, make sure Windows Form is selected.Set the
Name to PropertyEditor and click Add

Dialog Box Creation

To create a dialog box, you start with a form, which
you can get by creating a Windows Application or deriving a class from
Form. Here is an example:

There are a few actions you should perform on a form
to transform it into a dialog box; but normally, these are only
suggestions, not rules. Based on the Microsoft Windows design and
standards, to create a dialog box, you should set a form's
FormBorderStyle property to FixedDialog. Setting this property
changes the borders of the form to the standard borders of a dialog box
(the border of a dialog box is thinner than that of a regular form). You
can set this characteristic in the Properties window or programmatically.
Here is an example:

Besides taking care of the border, you should also set
both the MinimizeBox and the MaximizeBox properties to
False. This causes the window to display only the system Close button.
You can set these characteristics in the Properties window or
programmatically. Here is an example:

To transform the PropertyEditor form into a dialog box, in the
Properties window, change its characteristics as follows:
FormBorderStyle: FixedDialogStartPosition: CenterParent
MinimizeBox: FalseMaximizeBox: False
ShowInTaskbar: False

Design the dialog box as follows:

Control

Text

Name

Label

Property Type:

TextBox

TxtPropertyType

Button

Cancel

BtnCancel

Label

Bedrooms:

TextBox

TxtBedrooms

Button

OK

BtnOK

Label

Bathrooms:

TextBox

TxtBatrooms

Label

Monthly Rent:

TextBox

TxtMonthlyRent

Closing a Dialog Box

You should provide a way for the user to close the
dialog box. A dialog box should have at least one button labeled OK. This
button allows the user to acknowledge the message of the dialog box and
close it by clicking the button. If the user press Enter, the dialog box
should also be closed as if the OK button was clicked.

Accepting an Action

Often the user will be presented with various options
on a dialog box and may be asked to make a decision on the available
controls. Most of the time, if you are creating such a dialog box, besides
the OK button, it should also have a Cancel button. The OK button should
be the default so that if the user presses Enter, the dialog box would be
closed as if the user had clicked OK. Clicking OK or pressing Enter would
indicate that, if the user had made changes on the controls of the dialog
box, those changes would be acknowledged and kept when the dialog box is
closed and usually the changed values of the control would be transferred
to another dialog box or form. Keep in mind that you are responsible for
implementing this functionality.

To fulfill this functionality of the OK button, after
adding it to a dialog box (or form), open the AcceptButton combo
box in the Properties window for the form and select the name of the
button.

Practical
Learning: Accepting an Action

Click an unoccupied area of the form

In the Properties window, click the arrow of the AcceptButton
field and select BtnOK

Canceling an Action

The Cancel button is used to allow the user to dismiss
whatever changes would have been made on the controls of the dialog box.
The dialog box should also be configured so that if the user presses Esc,
the dialog box would be closed as if the user had clicked Cancel.

To fulfill this functionality of the Cancel button,
after adding it to a dialog box (or form), open the CancelButton
combo box in the Properties window for the form and select the name of the
button.

Besides the OK and the Cancel buttons, a dialog box
can be created with additional buttons such as Finish or Help, etc. It
depends on its role and the decision is made by the application developer.

Practical
Learning: Cancelling an Action

In the Properties window, click the arrow of the CancelButton field
and select BtnCancel

Display the first form

The Help Button

Besides the system Close button, if you are planning to
provide help on a dialog box, you can equip it with a Help button. To
support this, the Form class is equipped with a Boolean property named
HelpButton. The default value of this property is false. In the
Properties window, you can set it to True. If you are programmatically
creating the dialog box, you can access this property and set its value to
true. Here is an example:

When the user clicks the help button, the mouse cursor
becomes equipped with a question mark. Here is an example:

You can then write code so that, when the user clicks a
control on the dialog box, some guiding help is provided as a tool tip.

Modal and Modeless Dialog Boxes

Modal Dialog Boxes

There are two types of dialog boxes: modal and modeless.

A Modal dialog box is one that the user must first close
in order to have access to any other framed window or dialog box of the same
application. One of the scenarios in which you use a dialog box is to create
an application that is centered around one. In this case, if either there is
no other form or dialog box in your application or all the other forms or
dialog boxes depend on this central dialog box, it must be created as modal.
Such an application is referred to as dialog-based.

Some applications require various dialog boxes to
complete their functionality. When in case, you may need to call one dialog
box from another and display it as modal. Here is an example:

The Date and Time dialog box of WordPad is
modal: when it is displaying, the user cannot use any other part of
WordPad unless he or she closes this object first

After creating a dialog used as an addition to an
existing form or an existing dialog box, to call it as modal, use the
ShowDialog() method.

Modeless Dialog Boxes

A dialog box is referred to as modeless if the user does
not have to close it in order to continue using the application that owns
the dialog box. A modeless dialog box has the following characteristics

It has a thin border

It can be neither minimized nor maximized. This means that it is not
equipped with the Minimize or the Maximize buttons

It is not represented on the taskbar with a button

It must provide a way for the user to close it

Here is an example:

The Find (and the Replace) dialog box of WordPad
(also the Find and the Replace dialog boxes of most applications) is
an example of a modeless dialog box. If it is opened, the user does
not have to close it in order to use the application or the document
in the background.

Since the modeless dialog box does not display its
button on the task bar, the user should know that the dialog box is opened.
To make the presence of a modeless dialog box obvious to the user, it
typically displays on top of its host application until the user closes it.

A modeless dialog box is created from a form but it
should look like a regular dialog box or a tool window. Therefore, to create
a modeless dialog box, set the FormBorderStyle property to an
appropriate value such as FixedSingle, FixedToolWindow,
Sizable or SizableToolWindow. Also, set its ShowInTaskbar
property to False.

After creating the dialog box, to display it as
modeless, call the Show() method. The fundamental difference between
the ShowDialog() and the Show() methods is that the former
displays a modal dialog box, which makes sure that the called dialog box
cannot go in the background of the main application. By contrast, the
Show() method only calls the dialog box every time it is requested. For
this reason, it is up to you to make sure that the modeless dialog box
always remains on top of the application. This is easily taken care of by
setting the Boolean TopMost property of the form to True.

There are two main ways a normal modeless dialog box can
be dismissed:

If the user has finished using it, he or she can close it and recall
it at will

When the form or application that owns the modeless dialog box is
closed, the form or application closes the modeless dialog if it is
opened; this means that you don't need to find out whether a modeless
dialog box is still opened when the application is being destroyed:
either the user or the application itself will take care of closing it

An Application With Various Forms or Dialog
boxes

When you create a Windows Forms Application, the
starting form is made available to you. If one form is not enough for your
application, you can add as many as necessary. To add (or to create) a (new)
form, you have various options:

On the main menu, you can click Project -> Add New Item...

On the main menu, you can click File -> Add New Item...

In Solution Explorer, you can right-click the name of the project,
position the mouse on Add, and click Add New Item...

In the Add New Item dialog box and in the middle
section, click Window Form (.NET), provide a name in the Name edit box then
click Open.

If your application is using various forms and you want
to display a particular one at design time:

In the Forms Designer, you can click the tab that corresponds to the
desired form and that has [Design]

On the main menu, you can click Window and click the name of the
form in the list under Close All Documents

In Solution Explorer, expand the Header Files node if necessary and
double-click the name of the desired form that has the .h extension

If you visually add two (or more) forms to your
application, you may need to link them, allow one to call the other. To do
this, in the top section of the file, type #include followed by the
name of the header file in which the form was defined. In the section where
you want to access the form, declare a handle to the class of the form and
use the new operator to allocate memory for it. To display the other
form, you can call its Show() method.

Practical
Learning: Using Various Forms

Display the first form

Double-click the New Property... button and implement the event as
follows: